Compact liquid toner apparatus with straight through feed

ABSTRACT

APPARATUS FOR APPLYING A LIQUID TONER ONLY TO THE SURFACE OF THE SHEET OF PAPER OR THE LIKE FOR DEVELOPING AN ELECTROSTATIC IMAGE THEREON. THE PAPER IS FED IN A RECTILINEAR PATH WITH THE ACTIVE FACE THEREOF DOWN, AND THE PAPER FLOATS ON A MENISCUS OF LIQUIE TONER. IN THE PREFERRED EMBODIMENT THE PAPER IS POSITIVELY SPACED FROM THE SURFACE OF THE TONER DISTRIBUTOR BY A STRAND OF PLASTIC MATERIAL WOUND AROUND THE DISTRIBUTOR.

Nov. 23,1971 M. L. SUGARMAN ETAL 3,621,814

COMPACT LIQUID TONER APPARATUS WITH STRAIGHT THROUGH FEED 2 Sheets-Sheet 1 Filed July 11, 1969 Nov. 23, 1971 SUGARMAN EI'AL 3,621,814

COMPACT LIQUID TONER APPARATUS WITH STRAIGHT THROUGH FEED Filed July 11, L969 2 Sheets-Shoot 2 J14 Jfi 3 116 105 9% x m M a lit/6W5 @Zi".11.j ar'wzam (/26 @7 WV, Mm ,l fi

United States Patent 3,621,814 COMPACT LIQUID TUNER APPARATUS WITH STRAIGHT THROUGH FEED Meyer L. Sugarman, Northbrook, and Joseph H. Jaeger, Evanston, Ill. (both Apto/Graphics Inc., 512 Green Bay Road, Kenilworth, Ill. 60043) Continuation-impart of application Ser. No. 692,234, Dec. 20, 1967. This application July 11, 1969, Ser. No. 841,097

Int. Cl. B05c 3/00 US. Cl. 118-411 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for applying a liquid toner only to the surface of the sheet of paper or the like for developing an electrostatic image thereon. The paper is fed in a rectilinear path with the active face thereof down, and the paper floats on a meniscus of liquid toner. In the preferred embodiment the paper is positively spaced from the surface of the toner distributor by a strand of plastic material Wound around the distributor.

This application is a continuation-in-part of our copending application Ser. No. 692,234 filed Dec. 20, 1967 for Compact Liquid Toner Apparatus With Straight Through Feed, now abandoned.

The art of electrostatic printing is generally well known. In this art, either an insulating surface with selectively produced conductive areas (such as paper or metal coated with hotoconductive zinc oxide) or some other suitable plate or cylinder is used as a printing base, or a plate or roller capable of transfering electrostatic charge patterns is used. In the first case, the hotoconductive surface is electrostatically charged in the dark, and an image is projected optically thereon. Photoconductive properties of the light sensitive coating cause the charge to be dissipated where the coating is struck by light, and to rmeain Where it is not so struck. A toner of either liquid or dry nature then is applied to the base, and adheres selectively according to its nature either to the charged area or to the discharged area. The application of heat to bond toning particles to the base is generally necessary with a dry toner, but is not necessary with a liquid toner. With a liquid-type toner, the toner particles become affixed to the underlying surface, upon drying of the liquid suspension medium.

Typically, in prior art liquid toner apparatus, a supply of liquid toner has been maintained in a tank. Guides of one sort or another have been provided going in and out of the tank, and curved therethrough, to direct the electrostatically charged and exposed paper through the liquid toner in the tank. Generally speaking, squeegee rollers have been provided at the outlet from the tank to squeeze at least some of the liquid from the paper or other base. However, it is apparent in the dip systems that the base is exposed to a liquid toner on the back side as well as on the face side. Paper is the most common base material, and the paper becomes rather wet upon being passed through the toner. Squeegee rollers are not capable of removing all of the liquid, and it therefore has been necessary to provide relatively strong means for adequately drying the toned paper, such as infrared heaters, strong air pressure, or a combination thereof. This is obviously undesirable in that it requires an additional step of handling the paper, it requires drying room, and it delays availability of the finished print.

The rather well known arcuate toning apparatus as outlined immediately above is limited to the use of fiexble material, such as paper, for the printing base. This is necessary because the paper or other base must enter the liquid toner in the tank from the top, and also exit from the top, passing along a curved path in between. This prevents prior art liquid toning apparatus from being used on various rigid printing base materials, such as metal plates or heavy card stock materials. Also, the distance from entrance to exit, due to the curved path, seriously limits the minimum length of copy possible to be processed in such developer units.

Accordingly, it is an object of the present invention to provide a liquid toning apparatus having a straightthrough or rectilinear feed path for the exposed paper or printing base.

It is another object of the present invention to provide a liquid toning or developing apparatus wherein the exposed paper or other printing base is contacted by the liquid developer medium only on the electrostatically active or exposed face thereof.

More specifically, it is an object of the present invention to provide an improved liquid toning or developing apparatus wherein the exposed paper or other printing base is processed with its active face down, and wherein the printing base floats on a meniscus of liquid toner.

Additional objects and advantages of the present invention will be apparent to those skilled in the art when the accompanying drawings are considered in connection with the balance of the present specification, wherein:

FIG. 1 is a perspective view of a liquid toner apparatus constructed in accordance with the present invention:

FIG. 2 is a fragmentary perspective view generally similar to FIG. 1 and showing a modification of the invention:

FIG. 3 is a longitudinal view taken substantially along the line 33 in FIG. 2:

FIG. 4 is a perspective view of a commercially successful form of the present invention:

FIG. 5 is a longitudinal sectional view taken substantially along the line 55 in FIG. 4, and

FIG. 6 is fragmentary perspective view of the form of the invention shown in FIG. 4, and taken generally along the line 6-6 in FIG. 4.

Turning now in greater particularity to the drawings, and first to FIG. 1, there will be seen a liquid toning or developing apparatus wherein a work piece 12 comprises a sheet of paper or other printing base. The sheet may be in rectangular form, for example, letter or legal size, or it may be in the form of a continuous web with the web being severed after toning or development. The paper is fed in with its active face down, and following electrostatic charging and exposure, between an upper roller 14 and a lower roller 16, the two rollers gripping the paper between them. These rollers are driven by any suitable power source (not shown) and preferably are of a rather soft rubber or other material, preferably being nonconductive to avoid lateral dispersion of an electrostatic charge previously established on the working face of the paper. As will be understood the electrostatic typically may be produced heretofore, by electrostatic charging of the difference of the paper and partial dissipation of the charge by optical projection thereon, or by any other means of selectively producing electricity by the charge patterns, such as electrographic systems laying down charges only in desired areas of an insulating surface.

Spaced downstream from the rollers 14 and 16 is a pair of output or squeegee rollers 30 and 32. The lower squeegee roller 32 is preferably made of a hard insulating material, such a Bakelite (phenolic), or other hard non-conductive plastics, or of glass. This roller need not be constructed of solid insulating material, but may be provided with an insulating outer sleeve. A hard roller is desirable to minimize carry-out of liquid by the paper or other base 12. However, soft rollers may be used while retaining the other features of the present invention. The surface material of the rollers should also be selected so as not to attract the toner, either tribo-electrically or by adhesion. The upper output or squeegee roller 30 is of rubber. The rollers 30 and 32 are driven in synchronism with the input rollers 14 and 16, such as by a suitable belt and pulley drive (not shown). In each case, it is only necessary that one of each pair of rollers be driven, the other inherently being driven by surface contact with the moving sheet of paper or the like.

A liquid toner distributor 44 is disposed below the paper and almost, but not quite, in contact therewith. The distributor is in the form of a pipe having a plurality of small, closely spaced apertures 46 along the upper element thereof. Liquid toner exits from the distributor under positive pressure on to the under or active side of the paper. Alternatively, as will be understood, the holes could be merged into one long slot. The toner is fed into the tube or pipe 46, preferably centrally thereof (the opposite ends being closed) through a conduit 48 leading from a motorized pump 50. An open top sump 52 underlies the distributor 44 and the output rollers 30, 32 to collect liquid dropping therefrom, and additional liquid may be supplied thereto as necessary. An outlet conduit 54 leads from the sump to the pump, whereby the liquid is continuously recirculated. The paper is maintained out of engagement with the distributor 44, as by floating on a meniscus of liquid exuding through the openings 46. The amount of liquid applied to the paper or other base is in excess of that required for development, and collects against the roller 32 as a pond or lake of liquid 78 which drips back down into the sump 52. The base is shown as moving horizontally, but it will be understood that it can move down hill at an angle, or that it can move somewhat up hill. If the paper moves up hill, it will be appreciated that the movement must be such as to prevent liquid from running down in the opposite direction against the feed of the paper.

A somewhat similar but modified form of the invention is shown in FIGS. 2 and 3. Similar parts are identified by numerals similar to those used heretofore, to avoid prolixity of discussion, the suffix a being applied by way of distinction. Rather than being a tube or pipe, the toner applicator or distributor 44a comprises a trough of rectangular cross section having the top thereof closed by a fiat fine mesh screen 80 through which the toner exudes against the active under surface of the paper. The exuded tones floats the paper out of contact with the screen. Some improvement of toner distribution is to be found in this embodiment as opposed to that of FIG. 1.

A further embodiment of the invention that has found commercial acceptance is shown in FIGS. 4-6. Many parts are similar to those heretofore shown and described, and like numerals with the addition of the suffix b are used to identify such similar parts.

The direction of paper or other base feed in FIGS. 4 and is from left to right, as opposed to the right to left feed in FIGS. 1-3. Furthermore, a support plate or tray 82 is provided on the inlet side for guiding the paper between the input rollers 14b and 16b, while a receiving or discharge plate or tray 84 is provided on the output side to receive the processed paper from the output rollers 30b, 32b. The distributor 4412 in the present instance comprises a dual distributor comprising a first distributor section 86 and a second distributor section 88. The two sections are identical, and only the first section therefore need be described.

The first distributor section 86 comprises a rather large rectangular tank or trough 90 having an internal vertical baffle 92 slightly to the left of the center line, and having an open space at the bottom at 94. The first distributor section thus has a first chamber 96 and a second chamber 98.

The second chamber is closed at the top by an intensifier plate 100 about which more will be said later. A distributing manifold 102 in the nature of a pipe extends transversely across the chamber 98 relative to the direction of paper feed, and is provided with a series of exit holes 104 across the top. Preferably the pipe is rotatable about its axis for positioning of the holes 104, but it has been found that the best flow distribution is obtained with the holes at the top. Liquid toner is supplied to the manifold '102 through a conduit 106 from a pump 108 which receives liquid from a sump 110 through a conduit 112.

The top of the first chamber 96 is closed by a perforated plate 114 having a great many apertures therein. The apertures are on the order of .015 inch in diameter, but the size is not particularly critical. The particle size in the toner is measured in microns, and it therefore will be seen that the hole size is much greater than the particle size.

The perforated plate 114 and the intensifier plate 100 form a straight line continuation of one another, and are inclined downward slightly to the right about three degrees from the horizontal. (The paper is horizontal.) The downward inclination helps the liquid to flow, as does the movement of the paper, and the use of the imperforate plate following the perforated plate maintains the liquid developer in surface engagement with the active face of the paper for a longer time, and also produces a shearing or kneading of the liquid developer, therefore facilitating development.

As will be seen, the second distributor section 88 is spaced from the first section slightly as indicated at 116, whereby toner or developer from the first developer section may cascade down into the sump 110. Fresh developer or toner is applied to the under face of the paper by the second toner section, whereby to insure complete toning.

As will be seen to some extent in FIG. 4, but particularly in FIG. 6, a nylon monofilament line is wrapped around the developer or distributor units 86 and 88 as indicated at 118. This line positively spaces the paper from the perforated plate 114 and the intensifier plate insure that here will be no contact with the plates, should the weight of the paper tend to overcome the meniscus of material separating the paper from the plates. It has been found that engagement of the paper with the plates tends to cause smudging, probably due to partial dissipation of electric charges, augmented by physical activity of the toner in frictional engagement with the surface of the paper.

It will be seen in FIG. 4, that, considered in the direction of paper feed from left to right, the line along the top of the units 86 and 88 starts at the center as indicated at 120, and Works out in opposite directions in diverging relation. In other words, the line on the back section as viewed in FIG. 4 is wound with a right hand lead, while it is wound with a left hand lead in the front section as viewed in FIG. 4. This promotes lateral movement of the developer as well as movement in the downstream direction, thereby enhancing developer distribution and improving the quality of the developed image.

In accordance with the discloseure heretofore set forth the line 118 in the preferred embodiment is a nylon monofilament line. The strand could be metallic, or a multifilament wrap could be substituted, or embossed ridges could be provided. In addition, the perforated plate 114 could be provided with a transverse slot all of the way across in place of the perforations.

The feed of the paper or printing base is straight through. Thus, rigid printing bases can be used. Although paper is the most common base, the principles of the present invention apply also to metal, rigid plastic, etc. Although reference has been made particularly to toning or developing of images on electrostatically charged paper or the like. The principles of the invention are applicable also to chemical development and other processing of conventional photographic printing papers, such as those of the silver chloride, or silver bromide types. Since only the active face of the paper is brought in contact with the toner or developer, the paper is not wet on the back surface, or in any way soaked, whereby the squeegee rollers dry the, paper sufiic iently so that no special handling. is necessary. It also is to be noted that the squeegee roller contacting theactive face is preferably, although not necessarily, of an insulating material, whereby it does not dissipate charges before the toner has had an opportunity to set properly.

It is also to be noted that in many current development apparatus in which the paper is fed through a tank contalining developer, thereby wetting the back of the paper, not only is the handling of the wet paper difficult, but often unsightly markings are left on the back side of the paper. The present invention completely eliminates this back marking problem.

The invention is claimed as follows:

1. Apparatus for developing images such as electrostatic images comprising input feed means, output feed means, said input and output feed means feeding an exposed printing base along a predetermined path therebetween with the active face of the printing base down, developer distributing means immediately adjacent and below said path having a perforated upper portion for discharging developer therefrom, and a pump for applying positive pressure to developer in said distributing means to force developer from said distributing means upper portion under sufficient pressure and in sufiicient quantities to float said printing base on said developer above said distributing means, said distributingmeans comprising a tank having a substantially vertical baflle dividing the distributing means into an inlet manifold and an outlet manifold, the top of the outlet manifold being a substantially fiat, perforated plate and the top of the inlet manifold being a substantially flat irnperforate plate forming a continuation of said perforate plate and downstream thereof relative to the direction of printing base feed, and developer inlet means in said inlet manifold.

2. Apparatus as set forth in claim 1 wherein the imperforate plate is of greater extent than the perforated plate relative to the direction of printing base feed.

3. Apparatus as set forth in claim 1 wherein the printing base is substantially horizontal and the plates run downhill at a shallow angle relative to the horizontal.

4. Apparatus as set forth in claim 1 wherein the distributing means includes a secondlike tank spaced close to the first mentioned tank relative to the direction of base feed.

5. Apparatus as set forth in claim 4 and further including a strand wrapped around said distributing means a plurality of turns positively to space the printing base from the plates.

6. Apparatus for developing images such as electrostatic images comprising input feed means, output feed means, said input and output feed means feeding an exposed printing base along a predetermined path therebetween with the active face of the printing base down, developer distributing means immediately adjacent and below said path having a perforated upper portion for discharging developer therefrom, and a pump for applying positive pressure to developer in said distributing means to force developer from said distributing means upper portion under sufiicient pressure and in suflifiient quantities to float said printing base on said developer above said distributing means, said distributing means comprising a tank having a substantially vertical baffle dividing the distributing means into an inlet manifold and an outlet manifold the top of the outlet manifold comprising a first plane and the top of the inlet manifold comprising a second plane forming a continuation of and co-planar with the first plane and downstream thfe'reof relative to the direction'of printing base feed, said first plane being open for the flow of liquid developer therethrough and said second plane being closed against such flow.

References Cited UNITED STATES PATENTS 1,928,235 9/1963 Taylor -94 3,169,887 2/1965 York 118-637 3,435,802 4/1969 Nail 117-934 346,869 8/1886 Sherck et a1. 118-411 2,678,024 5/1954 Kresse 118-401 3,192,846 7/1965 Wright 118-637 UX 3,249,088 5/ 1966 Ostensen *118-637 3,407,786 10/1968 Beyer et a1. 118-411 X JOHN P. MCINTOSH, Primary Examiner 

